Automatic fire alarm



Feb. 10,- 1931.- J. R. LONGWORTH ET AL 59 AUTOMATIC FIRE ALARM FiledJan. 12, 1929 NVEA/m: "ZQW W Patented Feb. 10, 1931 UNITED STATES PATENTOFFICE JAMES ROBERT LONG-WORTH AND HERBERT HIRST, OFBOLTON, ENGLAND;SAID LONG- WOBTH ASSIGNOR TO SAID HIRST AUTOMATIC FIRE ALARM Applicationfiled January 12, 1929, Serial No.

This invention relates to automatic fire alarms and utilizes athermostatic device for closing an electric circuit, which will cause abell to ring or give other notification, while facilities are providedwhereby, for testingor other purposes, the electric circuit may beclosed.

A feature of the present invention is that we can readily utilize anordinary push button switch used in connection with an electric bell orother notification device and adapt it to serve also as an automaticfire alarm without detracting from the facilities of being manuallyoperated.

\Vhere there is no existing push button switch or where it is desirableto have the existing one replaced we then apply a slightly modifiedconstruction but still retain the ad vantage of manual operation.

In rooms where it is improbable that the switch will be frequentlyrequired to be operated by hand we may provide another modified type ofour invention, providing in this case for a fine adjustment of thethermostatic device. In this case however we still provide an extensionwhereby the devices may be operated by hand.

In order that our invention may be fully understood we hereinafterdescribe same with 30 reference to the accompanying sheet of drawings,in which Fig. 1 is a side sectional view showing a form of fire alarmand bell push switch constructed in accordance with our invention.

Fig. 2 illustrates a further modification of our invention.

Fig. 3 is a front view of the devices shown in Fig. 2.

In constructing our device in accordance with Fig. 1 we provide a base3* of msulatmg material carrying the usual normally spaced apartcontacts 8 and 8 connected respectively to the wires 10 and 9. Anannular member 3 is then threaded at one end into the base 3 andsupports a casing 2. This annular member is internally screwthreaded toaccommodate the threaded disc 11. Through an onfice in this disc extendsa spring actuated plunger 12 which has a flange 13 at one end and awasher 14 at the other. We insert a 332,187, and in Great Britain May25, 1928.

screw 15 into the end of the plunger adjacent to the contacts 8 and 8for actuating the former into contact with the latter. A screw 16 isfixed in the other end of the plunger 12 and forced into contact withthe part 4 of a thermostat by the spiral spring 12.

The thermostat may be constructed of any known type but preferablyconsists of two metal discs 4 4 joined at their edges with a volatileliquid such as alcohol between them. Extending from the disc 4 is aprojection 5 to which is secured a push button 6 which protrudes freelythrough the casing 2 which is preferably detachably mounted on themember 3 through the medium of the screws 2, said casing 2 preferablyhaving perforations 2 therethrough.

By pressing the button 6 the plunger 12 is moved inwardly against theaction of the spiral spring 12 and the screw 15 forces the contact 8into engagement with the contact 8, thus closing the electric circuitthrough the wires 9 and 10, the device thus functioning as an ordinarybell push switch. v

However, when a fire occurs, or when through other causes heat isgenerated in the vicinity, the liquid in the thermostat expands, causingthe disc 4* to move away from the disc 4 with the result that theplunger 12 is moved inwardly as above described and the electric circuitclosed, giving an alarm.

By removing the casing 2 the disc 11 can be screwed in or out on themember 3 to vary the tension of the spring 12 so that when the devicefunctions through the medium of the thermostat it will actuated atvarying temperatures to give the alarm. This is due to the differenttensioningof the spring giving more or less resistance to the movementof the disc 4 on expansion.

The modified device depicted in Figs. 2 and 3 functions in the samemanner as referred to above, but, in this instance, the easing 2 coversthe push button 6. An adjusting screw stud 5 is threaded through thecasing 2 and engages the push button 6. A pointer 5 is secured to theexposed end of this stud 5 and extends over suitable graduations 5 onthe casing 2. Although this modified form of device is intended for usewhere it is not desired to employ it as an ordinary push button switch,yet the circuit may be closed by turning the pointer 5* until thecontacts 8 and 8 are forced into engagement.

The normal purpose of the stud 5 and pointer 5 is, however, to vary thetension of the spring 12*, so that thedevice Will function under theinfluence of the thermostat at variable temperature, depending upon thesetting of the point. screwing inthestud 5 compresses the spring 12causing it to offer greater resistance to the movement of the disc 4* onexpansion. When the stud 5 is screwed in the reverse direction theopposite effect takes place.

Such being the nature and object oI" our saidrinvention What We claimis 1. Inan automatic fire alarm, in combination, a base, normally spacedapart electric circuit contacts on said base, an eXpansible thermostat,a plunger, including a spring, interposed between the thermostat and thecontacts, said'plunger adapted to force one contact into engagement withthe other upon expansion of the thermostat and acting against the actionof the spring, a casing enclosing theicontacts, thermostat andplunger,anda longitudinally adjustable disc in thecasing =for varyingithetension of the plunger: spring.

2. :In. an :automatic fire alarm, in combination, a base, normallyspaced apart electric circuitcontacts on-said base, anzexpansiblethermostat, aaplunger, including a spring, interposed between thethermostat and the contacts, said plunger adapted to force one contactinto engagement with the other upon expansion of the thermostat andacting against the action of the spring, a casing enclosing thecontacts, thermostat and plunger,

a longitudinallyadjustable disc in the casing for varying the tensionof'the plunger spring, ind means extending-exteriorly'of the casing forvarying the tension of the plunger spri'ng'to offer varying resistanceto the movement of the thermostat underexpansion.

3. :In an aut-omatic'fire alarm, in combination,a'base,'normally spacedapart electric circuit contacts on said base, an eXpansible thermostat,a plunger, including a spring, interposed between the thermostat and thecontacts, said plunger adapted to force one cont-act into engagementWith the other upon expansion of the thermostat and acting against theaction of the spring, a casing enclosingthe contacts, thermostat andplungor, and means extending cXter-iorly of the casing for varying thetension of the plunger spring to Oder-varying resistance to the movementof the thermostat under expansion.

4. In an automaticlire alarm,-in combination, a-base, normally spacedapart electric circuit contacts on said base, an internally threadedmemberrattached to said base, a longitudinally movable disc threadedinto said member, a plunger longitudinally movable in said disc, aspring for normally holding said plunger from the actuated position withrespect to the contacts, an expansible thermostat in engagement withone'end of the plunger, a casing attached to the internally'threadedmember, and a push button carried by the casing and connected to thethermostat.

' 5. In an'automatic fire-alarm,-in combination, abase, normally spacedapart electric circuit contacts on said base, an internally threadedmember attached to said base, a longitudinally movable disc threadedinto said member, a plunger longitudinally movable in said disc, aspring for normally holding said plunger fromtheactuated position withrespect to the contacts, an cxpansible thermostat in engagement with oneend of the plunger, a casing attached to the internally threaded member,a push button carried by the casing and connected to the thermostat, ascrew stud threaded through the casing, graduations on the exposed faceof the casing and a pointer secured to the screw stud. 1

JAMES ROBERT LONGIVORTH. HERBERT HIRST.

